Stroke - A Comprehensive Overview

Definition

Classification

Pathophysiology

Ischemic Stroke

• Normal CBF: 40-60 mL/100 g brain/min
• Below 16-18 mL/100 g/min: neurons become electrically silent but remain viable - this is the ischemic penumbra (salvageable)
• Below 10 mL/100 g/min: membrane failure, influx of extracellular K⁺ and intracellular Ca²⁺, irreversible infarct core forms within 4-10 minutes

Hemorrhagic Stroke (ICH)

1. Directly compresses/destroys surrounding tissue
2. Causes progressive perihematomal edema
3. Raises intracranial pressure (ICP)

Etiology of Ischemic Stroke

1. Embolism - from cardiac sources (atrial fibrillation, mural thrombus, valvular disease) or artery-to-artery (carotid plaque)
2. In situ thrombosis - of large or small (lacunar) intracranial vessels, often on atherosclerotic plaque
3. Hypoperfusion - flow-limiting stenosis causing watershed ischemia

Common Causes (Harrison's Table 438-2)

Sites of Hypertensive ICH (Rosen's EM)

Risk Factors

• Hypertension (most important)
• Atrial fibrillation
• Diabetes mellitus
• Dyslipidemia
• Smoking
• Carotid atherosclerosis
• Obesity, physical inactivity

Clinical Features

Anterior Circulation (ICA, MCA, ACA territory)

• Contralateral hemiparesis/hemisensory loss (face and body)
• Aphasia (dominant hemisphere)
• Neglect (non-dominant hemisphere)
• Homonymous hemianopia
• Gaze deviation toward the lesion

Posterior Circulation (Vertebrobasilar territory)

• Ipsilateral cranial nerve deficits + contralateral hemiparesis (crossed signs)
• Vertigo, diplopia, ataxia, dysarthria
• Wallenberg syndrome (lateral medullary stroke): vertigo, Horner syndrome, ipsilateral facial numbness + loss of corneal reflex, contralateral loss of pain/temperature
• PCA stroke: homonymous hemianopia, alexia without agraphia

Lacunar Syndromes (pure small-vessel disease)

• Pure motor hemiplegia (posterior limb of internal capsule/pons)
• Pure sensory stroke (thalamus)
• Ataxic hemiparesis
• Dysarthria-clumsy hand syndrome

Hemorrhagic Stroke

NIHSS (National Institutes of Health Stroke Scale)

Diagnosis

Initial Workup

1. Non-contrast CT head - first-line; immediately identifies hemorrhage, excludes ICH before thrombolysis. Ischemic changes appear 6-12 hours after onset
2. CT Angiography (CTA) - identifies large vessel occlusion (LVO), carotid stenosis, dissection; guides thrombectomy decision
3. CT Perfusion (CTP) - identifies penumbra vs. core in extended time windows (6-24 h)
4. MRI/DWI - most sensitive for early ischemia; preferred for posterior fossa strokes
5. ECG + troponin - concurrent myocardial ischemia in 3-20% of stroke patients; cardiac monitoring ≥48 hours to detect paroxysmal AFib
6. Labs: CBC, PT/INR, aPTT, glucose, BMP

Acute Management

Acute Ischemic Stroke

• Airway protection; maintain O₂ sat >94%
• Treat fever aggressively (worsens ischemic outcome)
• Glucose: maintain 60-180 mg/dL; avoid hypoglycemia and hyperglycemia
• BP: do not lower unless >220/120 mmHg (or >185/110 mmHg if giving tPA)
• Head of bed >30° (aspiration prevention); NPO until swallow assessment
• Pneumatic compression stockings for DVT prophylaxis
• Cardiac monitoring ≥48 hours

• Dose: 0.9 mg/kg IV (max 100 mg); 10% as bolus, remainder over 60 minutes
• Window: ≤4.5 hours from symptom onset (for otherwise eligible patients with disabling symptoms)
• Requires BP <185/110 mmHg before administration
• Risk of symptomatic ICH: 2-7%
• Tenecteplase is an alternative (single bolus; equal or superior efficacy in some settings)
• Goal door-to-needle: ≤60 minutes (target ≤45 min)

• Indicated for large vessel occlusion (ICA, M1-M2, basilar artery)
• Window: up to 24 hours from last known well with favorable perfusion imaging (DAWN/DEFUSE-3 trial criteria)
• Most effective treatment for LVO; NIHSS-guided selection
• Combine with IV tPA when both eligible

• Aspirin 160-325 mg within 24-48 hours (not within 24 h of tPA)
• Dual antiplatelet therapy (aspirin + clopidogrel or ticagrelor) for 21-30 days for minor non-cardioembolic stroke / high-risk TIA (then aspirin alone)

Hemorrhagic Stroke (ICH)

• Warfarin: Prothrombin complex concentrate (PCC) preferred over FFP (faster INR correction, lower volume, lower infection risk) + Vitamin K
• Dabigatran: Idarucizumab
• Factor Xa inhibitors: Andexanet alfa

Secondary Prevention

• Apixaban 5 mg BID (reduced dose 2.5 mg BID if impaired renal function)
• Timing: generally start within 2-14 days depending on stroke size and hemorrhagic risk

• Symptomatic carotid stenosis ≥50-70%: carotid endarterectomy (CEA) is first-line, ideally within 2 weeks
• Intracranial stenting reserved for recurrent stroke despite optimal medical therapy

• BP: target <130/80 mmHg
• Statin therapy (LDL lowering): all ischemic stroke patients
• Glucose control in diabetics
• Smoking cessation, weight management, physical activity

Complications

• Brain edema (peaks day 2-3, up to 10 days) - greatest risk in large MCA infarctions and young patients
• Hemorrhagic transformation of ischemic stroke
• Aspiration pneumonia (15-25% mortality; swallowing assessment mandatory)
• Post-stroke seizures and epilepsy (16-17x increased risk vs. general population; higher with cortical and hemorrhagic strokes)
• DVT/PE
• Cardiac arrhythmias (particularly AFib discovered after stroke)
• Post-stroke depression (~30% of patients)

Rehabilitation

• Speech therapy (aphasia, dysphagia)
• Physical therapy (motor recovery)
• Occupational therapy (ADLs)
• Psychological support